These coins were minted at a time surrounding the end of the first millenium (or THE millenium to the ancients), and it was "known" far and wide that the world was about to end. So, everyone got super pious and brought religion into every aspect of their everyday life... even making their coins, front and back, carriers of the image and message of God. It is said that upon the eve of December 31, 999 AD (Y1K), everyone packed into churches to spend the night, just to make sure they got a good spot on the way up to heaven.